System Dynamics Applications / 2 / 2.13

2.13 MODULE—EXPANDED DEFINITION

A module is a frequently encountered fundamental building block of system dynamics structure. The simplest models are built around a single stock (level or accumulator) with a small number of auxiliaries used for a specific calculation.

Modules make complete sense when they demonstrate a characteristic set of dynamic behaviours such as may be represented by an equivalent systems archetype. The rationale used in specifying modules is based on experience as much as logical definition according to a specific set of feedback mechanisms, or a frequently encountered systems archetype.

The choice of the boundary around a module takes into account factors such as the:

• nature of the phenomenon being modelled and the explanations provided in the system dynamics literature, such as Sterman (2000);
• ability of the software application to depict graphically the relevant stocks and flows within the model;
• likely connections to other modules;
• need for standardisation of module specifications; and
• way in which testing (verification) will be conducted.